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Trephination of the Frontal Sinus


Introduction

Trephination of the frontal sinus can be used in three ways. Traditionally, it was used for the drainage of acute processes such as a Pott’s puffy tumor or bacterial frontal sinusitis. Second, trephination can be combined with transnasal endoscopic approaches to the frontal sinus for severe inflammatory disease or challenging frontal recess anatomy, frequently referred to as a minitrephine. Finally, it can potentially obviate the need for an osteoplastic flap to introduce endoscopes and/or instruments to access far superior and far lateral inflammatory and noninflammatory conditions of the frontal sinus in select cases. This chapter discusses the use of trephination to instill water (minitrephine) or of the trephine as a portal to aid in the performance or outcome of an endoscopic sinus procedure.

Key Operative Learning Points

  • 1.

    Three-dimensional computed tomography (CT) analysis of the frontal sinus is essential before performing a frontal trephine ( Fig. 111.1A ).

    Fig. 111.1, A, Coronal computed tomography (CT) scan demonstrating right-sided frontal opacification with involvement of the anterior ethmoid sinus. B, Axial CT scan displaying the air-fluid level in the right frontal sinus.

  • 2.

    The landmarks for the trephine are the two supraorbital nerve foramina. A line connecting these two points is drawn, with an entry site ideally placed in the medial brow (see Fig. 111.1B ).

  • 3.

    Computer navigation can be helpful in performing a frontal sinus trephine.

Preoperative Period

History

  • 1.

    History of present illness

    • a.

      The patient being considered for frontal sinus trephination is one who has failed medical therapy and is a candidate for endoscopic sinus surgery with a current frontal sinus component.

  • 2.

    Past medical history

    • a.

      Prior endoscopic surgery

    • b.

      Status of the bony boundaries of the frontal sinus and orbits

    • c.

      History of facial trauma or external surgery for the frontal sinus

Physical Examination

  • 1.

    Nasal endoscopy to assess visualization of the outflow tract of the frontal sinus. This should include the presence of ipsilateral septal deviation and the size and configuration of the middle turbinate.

  • 2.

    Palpation of the forehead will give a general indication of the bony prominence of the frontal sinus and its likely extent above the brow.

  • 3.

    Palpation of the supraorbital foramina and testing of sensory function

Imaging

  • Maxillofacial CT scan reconstructed in three planes, preferably with navigation capability (see Fig. 111.1B )

  • The dimensions of the frontal sinus in sagittal, axial, and coronal planes should be reviewed on CT to establish the safe external position and depth of safe penetration for the trephine burr.

Indications

As endoscopic techniques have improved, so too has the ability of sinus surgeons to address frontal sinus pathology endonasally. The utility of frontal sinus minitrephine, therefore, has become increasingly limited. Frontal sinus trephination does, however, remain a valuable tool as a stand-alone procedure, as an adjunct to frontal sinus endoscopy, and also as a combined endonasal and external approach for the following indications :

  • 1.

    Inflammatory frontal sinus pathology that meets criteria for endoscopic sinus surgery after medical therapy has failed

    • a.

      Acute frontal sinusitis

    • b.

      Chronic frontal sinusitis

    • c.

      Pott’s puffy tumor (subperiosteal abscess due to osteomyelitis of frontal bone)

    • d.

      Mucocele

    • e.

      Mucopyocele

  • 2.

    Inability to resolve pathology with conventional endoscopic technique due to

    • a.

      Inspissated secretions

    • b.

      Altered nasofrontal anatomy (obstructing frontal cells, frontal recess scarring/stenosis and ossification)

    • c.

      Inaccessible pathology (far lateral and superior)

  • 3.

    Noninflammatory pathology of the frontal sinus

    • a.

      Osteomas

    • b.

      Fibrous dysplasia

    • c.

      Inverted papilloma

    • d.

      Repair of cerebrospinal fluid leak (CSF)

    • e.

      Posterior table frontal sinus fracture

    • f.

      Meningioma

Contraindications

  • 1.

    Frontal sinus trephination is contraindicated in the patient with a small shallow frontal sinus due to the risk of unintentional drilling through the posterior table. Approximately 15% of nonhypoplastic frontal sinuses will not accommodate safe trephination.

Preoperative Preparation

  • 1.

    Prepare the nose for traditional endoscopic surgery.

  • 2.

    Prepare the forehead to include surgical landmarks.

  • 3.

    Adjust the position of image guidance hardware if necessary to provide full access to trephine landmarks.

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